the health and economic costs of eating disorders are enormous. For example, obesity is associated with type 2 diabetes, cardiovascular disease, stroke, and cancer. Increasingly, the importance of the role of neuropeptides in appetite and energy'expenditure is being established. However, the high complexity of signaling pathways that regulate food intake and energy homeostasis makes the study of these critical mechanisms daunting. Therefore, it is not only necessary to develop advanced analytical methods to measure and identify these low abundance signaling molecules, but also to apply these methods to study the feeding circuit in a simpler well-defined system. The specific aims of this project include: (1) To develop novel mass spectrometry based strategies to enable enhanced in situ neuropeptide profiling and the first demonstration of quantitative direct tissue analysis and (2) To apply these innovative methods to investigate the differential display of neuropeptides in satiated and food deprived Cancer borealis (Jonah crab). The development of a mass spectrometry based method that allows quantitative comparison of neuropeptides in situ will enable increased sampling flexibility and reduced tissue processing thus decreasing the risk of analyte loss or contamination. Not only does the crustacean nervous system offer an excellent test-bed for this technology development and validation, but it is also an ideal model for investigating neuromodulation in a well-defined neural network. A high incidence of identified neurons whose electrophysiological properties can be readily assessed and a rich repertoire of neuromodulatory substances makes this small neural network an attractive model system. This project has great potential to lead to the discovery of new neuropeptides and increase understanding of the neurochemical basis of the peptidergic regulation of feeding behavior. Not only will the analytical methods developed be applicable to the study of larger, more complex vertebrate systems, but also the molecular insights gained from the study of the crustacean system will likely lead to the identification of homologous mechanisms in higher order species. Therefore, this study will lead to improved methods and extended capabilities for neuropeptide analysis as well as the identification of potential targets for the development of new pharmacologic treatments for eating disorders. *New methods for measuring molecular signals used by the nervous system will be developed and then applied to study how feeding behavior is controlled. This research will lead to a better understanding of nervous system principles as well as new treatments for important health concerns such as obesity. [unreadable] [unreadable] [unreadable]